1. Field of the Invention
The present invention relates to an inkjet recording apparatus and an inkjet recording method, and more particularly to an inkjet recording apparatus and an inkjet recording method of recording an image on a print medium by means of an inkjet recording head having a plurality of image recording elements.
2. Description of the Related Art
Japanese Patent Application Publication No. 4-18363 discloses an image forming apparatus having an inkjet recording head in which a plurality of recording elements are arranged, wherein a test pattern of a single color (density patch) in which the density changes in a stepwise fashion is formed on a recording medium, the densities corresponding to the positions of the ejection ports of the respective recording elements are read in by reading in the test pattern by means of a CCD line sensor, and density non-uniformities are corrected by correcting the drive conditions of the recording elements on the basis of the density data thus acquired. According to Japanese Patent Application Publication No. 4-18363, the density non-uniformity is measured respectively in each density region of the test pattern and therefore it is possible to correct density non-uniformities with high accuracy, in the whole density range.
Japanese Patent Application Publication No. 8-39795 discloses an inkjet recording method comprising a step of ejecting ink onto the recording medium and a step of ejecting a recording characteristics enhancing liquid which insolubilizes or aggregates the coloring material in the ink. Japanese Patent Application Publication No. 8-39795 discloses making, for recording primary colors (yellow, magenta, cyan or black) and secondary colors (red, green or blue), the ejection volume (the ejection volume per unit surface area on the recording medium) of the recording properties enhancing liquid ejected when recording secondary colors greater than the ejection volume of the recording properties enhancing liquid ejected when recording primary colors, in such a manner that a uniform chemical reaction between the ink and the recording properties enhancing liquid is achieved.
In an inkjet recording apparatus which records images on a recording medium (hereinafter, called “recording paper”) by means of an inkjet recording head having a plurality of image recording elements, non-uniformity correction is carried out using treatment liquid which insolubilizes or aggregates the coloring material in the ink.
In the inkjet recording apparatus described above, if the ink dots formed by droplets ejected from a plurality of nozzles are overlapping on the recording paper, then although sufficient treatment liquid is supplied for a dot ejected from a preceding nozzle, the supply of treatment liquid for a dot ejected from a succeeding nozzle is not sufficient. Consequently, the preceding dots are aggregated by the treatment liquid and their dot size is reduced, whereas the succeeding dots undergo insufficient aggregation and their dot size is large. If the ink ejected from a preceding nozzle and the ink ejected from a succeeding nozzle have different colors, for example, if cyan (C) ink and magenta (M) ink are ejected respectively from a preceding nozzle and a succeeding nozzle so as to print a blue (B) region, then the previously ejected droplet C is aggregated sufficiently by the treatment liquid, and therefore the dot size is always small. On the other hand, since the treatment liquid has been consumed by the previously ejected droplet C, then the aggregation of the subsequently ejected droplet M is insufficient. Consequently, the subsequently ejected droplet M has a large dot size in comparison with a case where only a droplet of the color M is ejected.
If the dot size varies as described above, then the visibility of non-uniformity also varies. The larger the dot size, the less visible non-uniformities become.
FIG. 17 is a diagram illustrating a schematic view of examples of density non-uniformities.
In FIG. 17, reference numeral 300 indicates a line head, and reference numerals 302-1, . . . , 302-8 indicate nozzles. Reference numerals 304-1, . . . , 304-8 indicate dots formed by droplets ejected respectively by the nozzles 302-1, . . . , 302-8. Furthermore, arrow S indicates the direction of relative conveyance of the recording paper with respect to the line head 300 (namely, the sub-scanning direction).
In the example illustrated in the “(a)” part of FIG. 17, an ejection defect occurs in the nozzle 302-5 and the liquid droplet volume is smaller than the originally intended liquid droplet volume. Consequently, the size of the dots 304-5 is smaller than the dots in other columns. Moreover, the depositing positions of the dots 304-5 are displaced toward the right in the diagram from the originally intended depositing positions 306-5. Therefore, a stripe-shaped non-uniformity (banding) occurs at the position of the dots 304-5.
However, as illustrated in the “(b)” part of FIG. 17, if sufficient treatment liquid is not supplied (for example, when printing a secondary color), then the dot size becomes larger. Therefore, the overlap with the dots of the adjacent nozzles becomes greater, and the banding becomes more readily visible.
Consequently, the dot size varies and the visibility of non-uniformity changes between a case where non-uniformity is measured using a test pattern of a single color and an actual printing operation which includes secondary colors and tertiary colors. Therefore, it is not possible to respond to variation in the dot size during actual printing, by means of non-uniformity correction based on the measurement results of non-uniformity obtained using a test pattern of a single color.
Japanese Patent Application Publication No. 4-18363 measures density non-uniformity using a test pattern of a single color, and does not contemplate the relationship between preceding and succeeding nozzles when printing secondary colors or tertiary colors. Consequently, in Japanese Patent Application Publication No. 4-18363, the appearance of non-uniformity when printing secondary colors and tertiary colors differs from the measurement of non-uniformity using a test pattern, and therefore the accuracy of non-uniformity correction declines.
Japanese Patent Application Publication No. 8-39795 makes the ejection volume of a recording properties enhancing liquid when recording of a secondary color greater than when recording a primary color, but since the amount of solvent increases when recording a secondary color, then problems of cockling and curling occur. Furthermore, if the recording properties enhancing liquid is applied to recording paper by using a roller, then it is not possible to change the application volume of the recording properties enhancing liquid between a region where a primary color is to be recorded and a region where a secondary color and a tertiary color are to be recorded. Therefore, the concept of Japanese Patent Application Publication No. 8-39795 cannot be applied to such cases. Furthermore, problems of cockling and curling occur if the application volume of recording properties enhancing liquid is increased over the whole surface of the recording paper. Moreover, in the case of a recording paper having low permeability, there may be problems such as the occurrence of movement of the ink due to the recording properties enhancing liquid and increase in the drying load.